Another reason I like shear panels is simply that they are easy means to keep out the breeze.
Think of all the places that need to be blinded off from the outside.
For example, floor pans and bulkheads.
By laminating up a few layers(this panel can be contoured) you can incorporate/integrate comb inside, or foam strips.
These strips can be say 75mm wide, 6-12mm thick, in turn these form ribs, or members inside the panels making them extremely strong in bending forces, from something like a seat, or dash mounting point etc.
Within these foam or core ribs, you can add hard points for threaded inserts.
By using these CF shear panels, they allow you to do away with diag tube members, and all the other stuff you need to add in there in order to bolt a seat to.
I cant believe you can provide a mounting point, a diag brace, and a form of closing off the section, all in steel, or alloy, lighter than you can with CF panels.
Since the tooling budget needed for stamping, or hot hammering steel or AL alloy sheet into is insane, think milled steel tools, CF panels also excel here too.
All you need is a primed mdf tool, or cast epoxy to form CF panels of any shape.
If you steer away from hard tooling for forming steel panels, then your limited to panels fabricated in a more modular way either with welding, bonding, or riveting. This has drawbacks, weight, and limited to more angular forms(stress risers) being the main two that spring to mind.
For more info on CF forms with hard points, and details of fabricating CF items featuring hardpoints for inserts look at the links below.
They feature some r+d I did on two F1 CF constructions to get a little more insight in their construction.
Rear crash structure, Rear crash structure, a closer look. - Forum - F1technical.net
CF pushrod, with Ti bonded insert, Carbon Fibre pushrod, a closer look. - Forum - F1technical.net